Combustor for thermal power plants having toroidal flow path in primary mixing zone



June 17, 1952 A. J. NERAD 2,601,000

COMBUSTOR FOR THERMAL POWER PLANTS HAVING TOROIDAL FLOW PATH IN PRIMARYMIXING ZONE Filed May 23, 1947 4 Sheets-Sheet 1 4 @QQQQQQQQ 50 j 21 y46/5 6 o o e o s pob g cj 7/111 lIIlIIII/IIIII III/IIIIIII/IIII/I/IVIIIIIIIIIIIIIIIIIII/IIIIIII/IfiI/II/IIII/Ifl par/raw" Anthony J. Nerad,

His Attorn ey.

June 17, 1952 J NERAD 2,601,000

A. COMBUSTOR FOR THERMAL POWER PLANTS HAVING TOROIDAL FLOW PATH INPRIMARY MIXING ZONE Filed May 23, 1947 4 Sheets-Sheet 2 Y la P) R MFig.8

PLEN M C "BER semen rs INLET IVOZZLES Inventor:

\ Anthony J. N erad.

H is AU: own ey.

T lglz.

l 5% j 8O 7 0 r c w 2 c C Q Q 9 O E L w t o 0 Z 0 .0

Invento June 17, 1952 A J NERAD 2,601,000

COMBUSTOR FOR THERMAL I OWER PLANTS HAVING TOROIDAL. FLOW PATH INPRIMARY MIXING ZONE Filed May 23, 1947 4 Sheets-Sheet 3 Anthony J.Neraci His Attorney.

June 17, 1952 A. .1. NERAD 2,601,000

COMBUSTOR FOR THERMAL POWER PLANTS HAVING TOROIDAL IMARY MIXING ZONE 4Sheets-Sheet 4 FLOW PATH IN PR Filed May 25, 1947 mm His Attorney y J.Nerad,

Inventor: Anthem Z 61 #or 64858 Patented June 17, 1952 COMBUSTOR FORTHERMAL POWER PLANTS HAVING TOROIDAL FLOW PATH IN PRIMARY MIXING ZONEAnthony J. Nerad, Alplaus, N. Y., assignor to General Electric Company,a corporation of New York Application May 23, 1947, Serial No. 750,015

18 Claims.

This invention relates to apparatus for effecting heat releasingreactions between two fluid reactants. It has found particular utilityas a device for the combustion of fluid fuels in air, for instance as acombustor in a gas turbine powerplant, and is particularly well suitedfor small, high capacity, light weight combustors for aircraftpowerplants. This application is a continuation-in-part of myapplication Serial No. 501,106, filed September 3, 1943, and nowabandoned.

An object of the invention is to provide a fluid reaction device havinga new method of operation which gives greatly improved performancecharacteristics when used as a combustor for fluid fuels.

Another object is to provide a combustor for fluid fuels capable ofeffecting eiiicient mixing, ignition, and combustion under exceptionallydifficult conditions, and under an extremely wide range of heat releaserates, up to a maximum many times that though feasible with the mostadvanced combustion equipment known to the prior art, while employingapparatus which is simple and inexpensive to fabricate, small in sizeand light in weight, and capable of giving excellent performance with areasonable life expectancy.

Another object is to provide a liner arrangement for a reaction deviceof the type described having means for forming cooling and insulatingfluid strata over the interior surfaces exposed to the reactionproducts, which serves to prolong the liner life, reduce to a minimumthe deposition of carbonized particles when used as a combustor forfluid fuels, while permitting operation with extremely high combustiontemperatures.

Still another object is to provide an improved combustor capable of veryrapid changes in the rate of heat release without serious disturbance tothe combustion process. I

A further object is to provide a fluid fuel combustor arrangement whichfacilitates the initiation of combustion at high rates of air flow bymeans of an electric sparking device.

A further object is to provide a combustor capable of effecting readyignition and efiicient combustion over a ery wide range of combustionspace pressures, as is required in thermal powerplants for high altitudeaircraft.

The invention is particularly well suited for the combustion of a widevariety of liquid fuels, and may also be used with pulverized solidfuels entrained in a suitable fluid or with various other types of fluidreactants, such as those used with rocket or reaction motors.

Other objects and advantages will be apparent from the followingdescription taken in connection with the accompanying drawings, in whichFig. 1 is a longitudinal sectional view of a combustor embodying myinvention; Fig. 2 is a view on a larger scale of one end of thestructure shown in Fig. 1; Fig. 3 is a sectional view taken on the plane3-3 of Fig. 2; Fig. 4 is an end view of the fuel nozzle and adjacentchamber walls of the structure of Figs. 1 and 2; Fig. 5 is a sectionalview taken on the plane 5-5 of Fig. 4; Fig. 6 is a diagrammatic viewillustrating the basic theory of operation of the invention; Fig. 7 is asectional view taken on the plane 1-! of Fig. 6; Fig. 8, Fig. 9, andFig. 10 are diagrammatic representations of alternate methods ofsupplying a fluid uniformly to the reaction space; Fig. 11 and Fig. 12are views of combustors illustrating alternate arrangements for formingthe cooling and insulating fluid strata on the interior surfaces of thereaction chamber; Fig. 13 is a sectional View of a still furthermodified form of the invention; Fig. 14 is a sectional view on the planeI4l4 in Fig. 13; Fig. 15 is a view of a modification arranged to burnpulverized solid fuels; Fig. 16 illustrates diagrammatically how aplurality of combustors embodying the invention may be arranged in athermal powerplant such as a gas turbine; and Fig. 17 illustrates theinvention applied to an annular reaction chamber used as a combustor'fora gas turbine powerplant.

Referring first to the embodiment of the invention shown in Figs. 1-5inclusive, the combustion unit comprises two coaxial walls, an innerwall or liner [0 and an outer wall I I held in spaced relation to eachother by a number of circumferentially spaced axially extending fins l2which may be welded or otherwise fixed to either one or both of wallsIi] and II. The right hand portions of the unit walls 10 and l l aretapered and are connected together as is indicated at [3. In the presentinstance, the tapered discharge portion of inner wall [0 is formed as aseparate member I4 which telescopes over the main portion of the wall Hias is indicated at l5 and its end is in the form of a discharge nozzle16 which telescopes over and is loosely attached to member I4 bycircumferentially spaced clips l6 which may be welded to member [4 andengage over the end of nozzle Hi. This arrangement permits the parts toexpand and contract readily relatively to each other. Discharge nozzlel5 may supply gases to any desired point of consumption such as to thebuckets of a gas turbine wheel.

The forward or admission end of inner Wall [0 is closed by a head ll.The forward or admission end of outer wall H is closed by a head or domel8. Supported centrally in heads l1 and I8 is a fuel spray nozzle 19. At20 is a suitable spark plug for igniting the fuel-air mixture.

The fuel supplying means comprises a tubular nozzle 2| (Figs. 4 and 5)having a rounded spray tip 22 in which is a small discharge orifice 23.Nozzle 2| is supported in an outer casing 24 which at its one endprojects through an opening in head I! and its other end is providedwith a boss which fits in an opening in dome 18. Thus the nozzle casingis firmly supported in .the two heads. At 25 is a supply pipe throughwhich fluid fuel is supplied to the nozzle at a suitable pressure by apump or other means (not shown).

The space between walls and H and between heads I1 and [8 forms a plenumchamber .26 to which air is supplied by a conduit 21 from any suitablesource, such as an air compressor (not shown). In the case of a gasturbine powerplant, it may be an 'air compressor driven by a turbineoperated by hot gases from the combustion-unit.

In inner wall or liner 1.0 are a plurality of circumferentially spacedaxially extending rows of holes 28 through which combustion air passesfrom plenum chamber 26 to the axially elongated reaction space definedby inner wall I0. In the present instance, eight longitudinal rows ofholes are shown equally spaced circumferentially. However, a somewhatgreater or lesser number may be utilized, as noted more specificallyhereinafter.

The longitudinal rows of holes 28 terminate short of head I! (or}-otherwise stated, the first circumferential row of holes is spaced fromhead I 1) to define what may be termed an initial mixing and ignitionchamber 30 to which no air is directly discharged through the combustionair inlet holes 28.

It will be seen that the axial rows of holes 28 are arranged so thatcorresponding holes in the respective rows are in a common plane normalto the axis of the chamber. The fuel nozzle discharges fuel in a sprayinto chamber 30, the arrangement being such that the fuel is distributedin the form of a substantially hollow cone as shown at 35 in Fig. 2. Tothis end, a wide angle spray nozzle, that is, one giving a spray angleon the order of '80", is employed. It should be understood that nozzlesof other angles may be used; and for various modifications of combustordesign, nozzles having spray angles in the range from 50 to 90 have beenfound appropriate. The first ring of holes 28 is spaced from head 11 adistance such that fuel discharged from the spray nozzle does not reachthem, so that drops of liquid fuel are not discharged directly into thecomparatively cool entering air jets from the holes 28. To this end, thefirst ring of holes is spaced from the head I! a distance of the orderof .7 the diameter of the cylinder formed by wall l0, 1. e., .7 the meandiameter of the combustion space, but of course this spacing requiredwould vary somewhat with the spray angle of the nozzle used.

The fuel nozzle 21 has as its primary object the even distribution ofatomized fuel particles about the axis of the chamber and must beamenable to accurate flow rate control, preferably by means of varyingthe supply pressure. Uniform distribution of fuel over a wide range offuel 'flow rates is important, especiallywhere uniform temperatures aredesired across the exit of the combustion unit. Another desideratum foroptimum results is that the fuel be given a low forward or axialcomponent of velocity. This avoids hurling large droplets of fuelaxially down the combustion space at such high velocity as to giveinsufficient chance for mixing and burning.

In operation, fuel is supplied to chamber 30 by nozzle 2| and air issupplied through holes '28 to the combustion chamber.

The action which takes place is illustrated in Figs. 2 and 3 and will bedescribed more particularly in connection with Figs. 6 and '7. Airentering through each circumferential ring of holes flows insubstantially radial jets toward each other, meeting at the center ofthe combustion chamber. This is illustrated in Fig. 3 where 31 indicatesoutlines of the air streams flowing through a ring of holes 28 andimpinging into each other near the center of the combustion chamber, asis indicated at 32. Between the entering streams of air 3! aretriangular shaped spaces '33. From the center of the combustion chamber,the air turns and flows axially. From the first two or three rings ofholes next adjacent the mixing chamber .30 air flows axially toward endclosure head 11 :as indicated by the arrows .34, the flow toward thehead being confined to the central portion of the chamber. This axialflow is aided somewhat by the low pressure area created at the axis ofthe liner adj acent the nozzle by entrainment of air with the fluid fuelspray discharged from the nozzle. In Fig. 3, the heads of theapproaching arrows are indicated by dots surrounded by circles. As theair approaches the head, it spirals radially outward as is indicated bythe curved arrows 35. The fuel oil spray is indicated .at 36. The airflows transversely across this spray pattern picking up fuel particles,and this air with fuel particles mixed therewith flows axially asindicated by arrows 31, the flow being initially through thecomparatively unobstructed axial spaces 33. Air from the remaining ringsof holes 28, after impinging at the central portion of the combustionchamber, flows axially toward the discharge end of the combustionchamber. The fuel air mixture flowing axially from chamber 30, asindicated by arrows 31, becomes commingled with the air from suchremaining rings of holes, the final result being a complete and thoroughmixing of the fuel with the air and burning of the fuel.

The air from the initial openings 28 which flows axially towards thenozzle as indicated by arrows 34, 35 in Fig. 2 corresponds to what isordinarily called primary air" in the combustion art, while thatentering from successive openings and flowing axially toward the opendischarge end of the liner 10 corresponds to the secondary air.

The discrete jets of primary air are somewhat heated by radiation andconduction from, as well as some intermingling with, the burning gasesflowing in the direction of the arrows 3'! from the mixing and ignitionchamber through the spaces 33 between the entering jets of primary air.This preheating effect on the entering primary air has an importanteffect on the ignition characteristics, ease of starting, and ability tomaintain combustion under adverse conditions and over a wide range "ofair and fuel flow.

The air flow represented by arrows 34, 35 decribes a symmetrical opposedspiral or toroidal path in the space between the end plate I1 and thefirst circle of holes 28. This toroidal flow will herein be referredtoas the tore.

The chamber 30 defines adjacent to the fuel nozzle a zone of highlyturbulent flow relatively independent of the load on the combustionunit, which serves to maintain combustion, thoroughly entraining andmixing the fresh cool fuel from the nozzle. Once burning has beenestablished in this ignition space, the flame will not be extinguishedby material or rapid changes in fuel and air flow rates. Asdemonstrative of this fact, in such a chamber there has been burned fuelat varying rates of flow in the ratio of 1 to 100 without extinction ofthe flame and with high efficiency.

This arrangement accomplishes another important result. Ignition isreadily initiated by means of an electric spark due to the goodvaporization of the fuel entrained in the air comin in jets through thefirst ring of holes due to the preheating effect noted above. This fueland air mixture forming the tore is readily ignited by the spark andthis is accomplished over the full range of air flows and under verydiflicult operating conditions.

My improved construction results in the creation of the above-describedmixing tore and avoids the disadvantageous condition present in manyprior art devices wherein jets of cool incoming air get behind theincipient flames and blow them entirely or partly out. If blown out,

combustion ceases; if blown partly out, noisy and irregular or partiallycompleted combustion results. The provision of the tore chamber 30,without any holes 28, has the additional advantage that any large dropsof fuel thrown from the nozzle are not projected directly through theair inlet holes 28, since the fuel nozzle is selected with a spray anglesuch that the spray cone 36 intersects wall l0 between the head I! andthe first circumferential row of holes 28.

This provision of an initial mixing chamber to which no air is directlydischarged through holes 28 is a very important feature of my invention.It forms a cul-de-sac into which the fuel oil is sprayed and into whichair flows in a definite symmetrical path to effectively pick up the fuelparticles, mix with and vaporize the fuel and initiate burning. It isimportant that the holes 28 be so sized and spaced that in operation theair forms a stable ignition tore, and that thorough mixing of freshfuel, air, and burning combustion gases take place with a relativelysmall loss in total fluid head.

The precise arrangement, location, size and number of the holesdetermines the strength H of the tore, and thereby determines thequality and efficiency of the combustion as well as the capacity. Theholes 28 are spaced apart axially and circumferentially by distancessuch that discrete jets are formed, as shown in Fig. 3, by the air fromthe annular space about the inner wall I0 flowing through these holes.The very eifective action of a free jet in mixing with and entrainingambient fluid is well known to those familiar with fluid flow phenomena,and the mixing is of great rapidity. I have determined that the holes 28should have diameters of the order of .1 the diameter of the combustionspace formed by wall If), i. e., the inner diameter of the liner, andthey should be spaced apart circumferentially between centers bydistances of the order of /8 to /6 of the circumference of suchcylinder. The holes may be spaced axially a distance of the order of 1%hole diameters between centers or a distance of the order of A; thediameter of the combustion chamber between centers. Such an arrangementgives the necessary mixing space adjacent each free jet and at the sametime avoids excessive length of liner I0. Excess length of inner wallII], it has been found, results in higher liner wall temperatures.

To prevent deposit of carbon on the inner walls of the combustionchamber, I provide means whereby these surfaces of the walls are sweptover continuously by thin sheets of cooling and insulating air. To thisend, I provide slots 40 in wall I0 between the rows of holes 28 withwhich are associated deflecting plates 4| for directing air flowingthrough the slots in an axial direction along the inner surfaces of wall[0 between the axial rows of holes 28. The slots and deflecting platesmay be formed by making U- shaped cuts in the wall and bending thetongues so formed slightly inwardly, as shown particularly in Fig. 1. Asufficient number of slots 40 are provided, and they are made of such awidth, that there flows over the inner surface of wall Ill an envelopeof air in volume and extent sufflcient to prevent deposits of carbonfrom forming on the inner surface of the wall. This envelope of cool airalso serves to cool the liner wall.

To prevent deposits of carbon on the inner surface of end closure headI1, I provide air admission openings 42 in head I! around wall 24 and,in front of the openings, a deflecting plate 43 attached to the innerend of wall 24 by welding or other suitable means. Air flowing throughopenings 42 strikes deflecting plate 43 and is fanned out to flowradially outward across the inner surface of head H to cool it andprevent carbon deposits from forming thereon.

To likewise prevent formation of carbon deposits on the end of the fuelnozzle tip 22, a second deflecting plate 44 is located in front ofdeflecting plate 43 and provided with openings 45 located to directstreams of air across the face of the fuel nozzle, deflecting plate 43being provided with openings 46 for flow of air into contact withdeflecting plate 44. Deflecting plate 44 is of lesser diameter thandeflecting plate 43 and may be formed integral with it as shownparticularly in Fig. 5. It serves also to direct air across the adjacentsurface of deflecting plate 43 to prevent carbon from depositingthereon. A series of openings 41 adjacent the outer circumference ofhead I! effects flow of air in the direction of the arrows in Fig. 2over that portion of the surface of liner H] which defines the mixingtore chamber 30, thus keeping it clear of carbon deposits.

With the foregoing arrangement, there is provided a protective envelopeof air which flows over the inner surfaces of head I! and wall Ill andover the exposed surfaces of the fuel nozzle to prevent formation ofcarbon deposits on such surfaces. This envelope is thin relative to thediameter of the combustion chamber, thus avoiding any material effect onthe temperature of the outflowing gases. For example, the slots 40 maybe of a radial width such that the air envelope has a thickness of theorder of 1% of the diameter of the combustion chamber.

It should be noted that the quantity of carbonpreventing air enteringthrough slots 40, holes 42, 46, and 41 is small compared with thecombustion air which enters through the holes 28. The function of theair envelope is not primarily to furnish air for combustion but toprovide a fluid shield for preventin unburned or partly burned fuelparticles from contacting the comparativeiy cool metal walls of liner Iand other interior surfaces and'carbonizing thereon. It will also beobserved that the air entering the carbon-preventing openings 42, 4t, 47does so in a direction to complement and augment the tore in chamber'39. By arranging these auxiliary air inlets properly, an appreciablestrengthening of the toreis obtained.

It is necessary to operate my combustion chambeer with an air sup-ply tothe plenum chamber defined by walls I!) and II which is very uniformlydistributed, not rotating about the axis of the chamber or havingVigorous eddies. In a gas turbine application, such ideal conditions arenot always met. In order to rectify such conditions, a number ofperforated metal strips I2 may be provided which in width extend fromwall In to wall 'II and 'in length are approximately two thirds of thelength of inner liner II The result of the use of such means forrectifying the flow in. the annulus is to improve the uniformity of airsupply to holes 28, markedly, noticeably shortening the flame,increasing the capacity, widening the useful range of operation andextending the ignition" range. In other words, the function of theperforated baffles I2 is to smooth out the flow and make completelyuniform the how of airin the annulus.

With this arrangement for insuring a uniform supply of air to the holes28, the jets from a given circumferential row of holes 26 will meetexactly in the center of the chamber, as shown in Fig. 3, and thentravel axially as represented by the arrows in Fig. 2.

The design of reaction chambers employing the new principles of myinvention may be rationalized as follows:

The most elemental form of the invention is represented in Figs. 6 and7, which show two pairs of parallel, fiat, opposed wall members Hi0,IEBI, and I82, I03, respectively, defining an elongated combustion spacehaving a rectangular cross-section of width 10 and a height d, asindicated in Fig.7. Let the opposed walls I63, IEiI each be providedwith .a single combustion air inlet port I06 and IE5, respectively,which may be considered to be round holes, Assume now that air issupplied by a suitable compressor to the space surrounding the wallsIEO, lill, I62, I03. Air will begin to flow through the ports I0 3, 15as soon as a pressure difierence is established between the space 26 andthe combustion space defined within the walls. space 26 is assumed to besuch that it diffuses uniformly around the combustor walls at a commonstatic pressure 190, the fluid velocity in the space 26 being so smallthat the velocity head is negligible. Let it be assumed also that thecombustion space is at a uniform static pressure pc substantially equalto ambient atmospheric pres sure.

For small values of the pressure ratio QJO/Pc, the spouting velocity ofthe opposed jets formed by the orifices I65, I85, represented by thevectors V1 and V2, will be small. Because of the wellknown entrainingaction of a free jet, the spouting velocity is soon dispersed. In otherwords, the discrete opposed jets V1 and V2 extend only a short distancefrom the walls I60, IIH into the combustion space. If now the pressureratio goo/1 c is increased, the magnitude of the spouting velocities V1,V2, increases, and the length of the free jets also increases until theymeet at the The supply of pressure fluid to the center of the combustionpace. Because the fluid is supplied to the space 26 at a uniformpressure 220 with substantially zero velocity of approach" to thenozzles I04, I05 the jets represented by the vectors V1, V2 will beexactly normal to the walls I00, IBI and therefore they will be coaxial,so as to meet at the center of the combustion space.

It may be noted that as the pressure ratio across a simple sharp-edgeorifice increases, the length of the free jet produced also increases,as described above, until a certain maximum length is attained,whereupon further increase in the pressure ratio will produce no furtherincrease in the length of the jet. This maximum length of jet is also afunction of the diameter of the orifice, indicated as a in Fig. 6. Inpracticing my invention, the distance d between the opposed orifices IM,I should be so related to the orifice diameter a that the discrete jetsproduced by the orifices are sufficientl long that the jets V1 and V2actually meet at the center of the combustion space with an appreciableresidual velocity. When this happens the fluid fans out" laterally, asindicated by the stream-lines in Figs. 5 and 7. Thus the spoutingvelocities V1, V2 are converted into transverse velocity components V3,V4, V5, V6, as represented by the vector arrows projecting radially fromthe point of intersection of the jets V1, V2. Since the velocities V1and V2 were equal in magnitude and exactly opposed in direction, thevelocities V3, V4, V 5, V6, will likewise tend to be equal to each otherin magnitude and radiating uniformly from, and normal to, the commonaxis of the jets V1, V2.

From a consideration of Fig. '7 it will be seen that the fluidrepresented by the velocities V5, V6 will directly impinge on the sidewalls I02, I03 and will again fan out transversely as indicated by theflow lines. The magnitude of the velocities V3, V4, V5, V6, depends uponthe magnitude of the spouting velocities, V1, V2, and the efficiencywith which these velocities are converted into the transverse velocitycomponents. If the velocities V5, V6 are of suflicient magnitude, thefiuid may flow along the walls I92, I93 as represented by the flow linesand arrows I06, and may actually recirculate and be partially entrainedby the jets V1, V2, as indicated by the arrows Ill'i.

Now let one end of the combustion space he closed by means of atransverse plate inserted at the location of the plane I09 in Fig. 6.The fluid fiow represented by the axial velocity V2 will now impinge atthe center of the end closure plate I99 and fan out as indicated byarrows I I0. With suitable velocities, this fluid will likewiserecirculate as indicated by the flow lines, some of it being entrainedwith the jets V1, V2 as indicated by the arrows II I. That fluid whichis not so entrained will flow in a generally axial direction past thejets V1, V2 through the comparatively unobstructed spaces I I2 definedbetween the jets V1, V2 and the side walls I02, I03 as represented bythe arrows H3.

The resemblance between this basic flow path produced by the orificesI04, I05 in Fig. 5 to that described in connection with Fig. 2 abovewill now be seen. The reverse axial flow represented by the vector V3establishes a double opposed spiral flow path in the zone 38, which maybe considered to be two oppositely rotating vortices. Fluid iscontinually fed to these vortices from the entering jets V1, V2, acorresponding amount of fluid leaving each vortex as represented by thearrows I I 3.

If new liquid fuel particles are injected by suitable means into theopposed vortices represented by arrows I I0, I I I, the fuel will bevaporized or further broken up and mixed by reason of the high velocityin the vortices. After combustion is initiated, the burning mixtureserves to preheat the comparatively cool incoming jets V1, V2 byradiation, by conduction, and by partial entrainment with the fluidrepresented by the arrows III, II3.

It has been found that in order to produce discrete jets which meet atthe axis of the chamber so as to create a strong reverse axial velocityV3, the distance d between the opposed nozzles I04, I05 should be on theorder of ten times the diameter of the nozzles, when the nozzles areround in shape. It should be understood, however, that the nozzles neednot be exactly round but may be rectangular or other elongated orelliptical shapes. Orifices of such other shapes should preferably havethe same hydraulic diameter as an equivalent round orifice. Thehydraulic diameter may be defined as equal to four timesthe hydraulicradius. As is well known, the hydraulic radius is equal to thecross-section area of the orifice divided by its wetted perimeter. Itfollows that for orifices of shapes other than circular, the followingrelation should be approximately adhered to:

where d=distance between opposed orifices, as in Fig. 7.

A=cross-section area of the orifice used. P=wetted perimeter of theorifice used.

to secure efficient entraining action, the side walls I02, I03 should bespaced from the axis of the jets by a distance approximately .Zd. Withround orifices, this means that the spacing from the side wall to theedge of the orifice should be at least .15d. In cylindrical combustors,as in Figs. 1, 11, 12, 13, etc., good transverse spacing between jetsWill be obtained if the holes are arranged at to A; the circumference,measured between centers. It is however entirely feasible to use onlytwo opposed orifices, as in Figs. 6 and '7, or four holes; but six ormore have been found preferable.

I have also ascertained that the optimum spacing of the initial airinlet ports I04, I05 from the plane of the end closure I09 is on theorder of .7d. This axial spacing of the initial jets V1, V2 from theclosed end furnishes sufficient volume for the establishment of thedouble spiral opposed vortices. While greater spacing of the initialjets from the closed end may be used, this requires also a higherpressure drop in order to obtain a velocity component V3, which will bestrong enough to persist all the way to the end closure I09 and thenproduce the transverse opposed velocities IIO. A further considerationaffecting the minimum spacing of the first nozzles from the end closureI09 is that a suflicient time interval must be provided for the fuelparticles to mix with the air and begin burning. If the axial spacing ofthe initial jets from the closed end is too small, then the combustionprocess will not be sufficiently well established by the time thefuel-air mixture reaches the jets V1, V2 and the comparatively coolincoming jets will tend to blow out the burning mixture. It appears thata space of the order of .7d is the optimum required to effect efiicientignition and combustion with a minimum overall pressure drop.

So far, in the above discussion relating to Figs. 6 and 7, .it has beenconsidered that there were only two opposed orifices, I04, I05. Assumenow that a second set of opposed orifices H4, II5 be added, as indicatedin Fig. 6. These orifices are arranged similarly to I04, I05, but arespaced axially downstream by a distance 12, measured center to center.This second set of opposed orifices will produce jets represented by thevectors V1, V8 which are equal in magnitude to V1, V2 and are likewiseexactly normal to the axis of the reaction space. These jets will meetat the axis and tend to separate and flow axially in opposite directionsas represented by the vectors V9, V10. It will be apparent from Fig. 6that the vector V9 is in direct opposition to the vector V4, so that theeffect of the former is to decrease the latter. The result is that thevector V3 is increased, which means that more air from the first set oforifices I 04, I05 is caused to flow axially to the left. If now stillanother set of openings H6, H1 is added, the jets V11, V12, will produceaxial velocities V13, V14. The vector V13 will likewise react withvector V10 so as to cause more air from the initial set of nozzles toflow to the left into the opposed vortices in chamber 30. It will thusbe seen that adding additional axially spaced sets of nozzles has theeffect of increasing the flow of fluid into the vortex chamber 30.

A certain minimum spacing, b in Fig. 6, is re quired in an axialdirection between the orifices. This minimum depends upon the spacerequired to produce effective entraining action of the free jets withthe surrounding fluid. The axial spacing required between orifices isconsiderably less than the transverse or circumferential spacing (Fig.3), by reason of the fact that the transverse spacing must also be greatenough to form the comparatively unobstructed longitudinal flowpassages, represented at 33 in Fig. 3 and at I 22 in Fig. 7, to permitthe flow of burning mixture from the chamber 30 to the exit of thecombustor with a minimum pressure drop. It has been found that whenround orifices are used, a desirable axial spacing is in theneighborhood of 1 times the hole diameter measured between centers,which gives a spacing between jets of times the hole diameter. Themaximum axial spacing between orifices is determined by the desirabilityof keeping the overall length of the combustor to a minimum in order toconserve space. It has also been found that too great an axial spacingmakes the liner more diiiicult to cool.

The total number of holes depends upon the aggregate orifice areanecessary to pass that quantity of primary and secondary air, withoutexceeding the allowable pressure loss, which is required to complete thecombustion process and then reduce the average temperature of thereaction products to a value which the structure of the combustor exitand other. parts associated therewith may safely'be subjected to. Itwill be appreciated by those skilled in the art that in modern gasturbine powerplants its is necessary to introduce a certain quantity ofair in excess of that required for good combustion in order to dilutethe combustion products to a temperature which the turbine wheel willWithstand. As described more particularly hereinafter, a rule of thumbwhich may be used to determine the aggregate orifice area is that thetotal hole area should be that required to make the overall pressuredrop through the combustor roughly equivalent to 1% of the total head ofthe fluid supplied to the combustor. It has been found that combustorsmeeting this requirement give good combustion efiiciency with a minimumcost in terms of loss of pressure energy.

Tests of an actual combustor with a plurality of axially spaced nozzlesshow that substantially all of the air from the first set of nozzlesflows axially into the vortex chamebr 30. Likewise some, or perhaps all,of the fluid entering from the second set of nozzles I I4, I I5 willflow to the left into the vortex chamber. However, at some axiallocation there will be noted a division, fluid entering through nozzlesto the left of this location going into the vortex chamber 30, Whilejets at the right of this location flow to the right. This divisionpoint is'shown quite clearly in Fig. 2 as located between the second andthird sets of orifices, As noted hereinbefore, that fluid which flowsleftward into the vortex chamber 30 is what is ordinarily known in thecombustion art as the primary air, while that which fiows to the rightcorresponds to the secondary air.

Attention is directed to the fact that Figs. 6 and '7- representdiagrammatically the nature of the flow path. The stream lines and thevector arrowsrepresenting fluid velocities have not been drawn withmathematical exactness to represent actual magnitudes, but are merelyillustrative.

It will now be seen that the fluid velocities in the opposed vortices inthe initial mixing chamber 30 depend upon the magnitude of the initialspouting velocity V1, V2, the efiiciency with which this initialvelocity is converted into the axial component V3, and the effect ofsubsequent jets V7, V8, V11, V12, etc., as described above. On the otherhand, the shape or symmetry of the vortices depends upon the directionof the jets V1, V2, V7, V3, etc., the direction of the first set of jetsV1, V2 being particularly important. In order to form a uniformsymmetrical vortex fiow pattern,

it is necessary that the axial velocity component V3 be parallel to theaxis of the reaction space in order that the fluid will approach the endclosure member I09 in a direction perpendicular thereto, so as to divideevenly and produce the transverse oppositely directed velocities IIO. Toproduce this uniform symmetrical flow pattern, the supply of air to theorifices I04, I05, etc. must be entirely uniform, both with respect tothe static pressure 190 at which the fluid is supplied to the orifice,and with respect to the velocity of approach to the orifices. If the airsupply is not uniform, the jets will not meet properly at the axis ofthe combustion space and will produce axial velocities which are highlyerratic and unpredictable, both in magnitude and direction. When thishappens, the vortex flow pattern in chamber 30 may either be distorted,that is, unsymmetrical, or it may not be formed at all. Formation of astrong, symmetrical vortex flow patsupply is illustrated in Fig. 9.

tern in chamber 30 has been found essential to optimum performancerelative to ready ignition, wide range, and efficient combustion. Withan erratic, unstable, or unsymmetrical fiow pattern, the liberation ofheat in the combustion chamber is less uniform, ignition and combustioncharacteristics are poorer, and hot spots may be formed which veryshortly result in destruction of the liner.

There are many ways by which the required uniformity of air supply tothe orifices may be obtained. The simplest is shown in Fig. 8. Thisrepresents diagrammatically a compressor supplying air at a suitablepressure to a plenum chamber I08 of comparatively large volumesurrounding the end portion of the combustor liner H8. The comparativelyhigh velocity stream of air from the compressor will diffuse uniformlythroughout the generously proportioned plenum chamber, so that thevelocity with which the air enters the plenum chamber is substantiallydissipated and the total pressure is equivalent to the common staticpressure 720, which exists throughout the plenum chamber. Thus there isobtained a uniform air supply as was assumed above in connection withFigs. 6 and 7,

Another arrangement for insuring uniform air Here the liner H9 isprovided with short radially extending pipes I20, I2I connected to therespective orifices I04, I05. Each of the. radial pipes is connected byseparate conduits I22, I23 to the discharge scroll or diffuser of thecompressor. Thus if the compressor is arranged to discharge airuniformly into the conduits I22, I23, uniformity of the velocity ofapproach in the pipes I20, I2 I is assured. Because the pipe sectionsI20, I2I are exactly radial, this velocity of approach will be normal tothe axis of the liner and the jets produced will meet exactly at theaxis as desired.

Still another arrangement for uniform air supply is illustrated in Fig.10, in which the liner I24 is surrounded by an outer housing I25defining a comparatively restricted air supply passage I26. Thecompressor supplies air through the diifuser or transition section I2'Ito the pasage I26. Each of the air inlet orifices in liner I24 isprovided with a short radially extending nozzle pipe I28, each formedwith a well-rounded inlet. The efiect of these nozzles I28 is somewhatthe same as that of the short, straight sections of pipe I20, I2I inFig. 9. With the arrangement of Fig. 10, the jets produced will be verynearly exactly radial, regardless of any non-uniformity in the airvelocities through the space I26. It has been found that nozzles such asthose indicated in Fig. 10 make the combustion device less sensitive tovariations in the direction or velocity at which the fluid in thetransition section I-2'I approaches the liner I24. A combustor inaccordance with my invention and embodying the improved nozzlearrangement of Fig. 1 0 is disclosed more fully in United States PatentNo. 2,510,645, issued June 6, 1950, on an application, Serial No.705,866, filed October 26, 1946, in the name of Kenton D. McMahan andassigned to the same assignee as the present application.

Another particularly effective, yet structurally simple, method forobtaining uniformity of air supply is the perforated bafile arrangementshown in Figs. 1, 3, and 13, 14. It will be obvious to those skilled inthe art that many different arrangement of bafiles, shrouds, guidevanes, honeycomb grids and similar known 'ex-, pedients may be used tomake sufliciently uni- 13 form the flow of air to the inlets of theliner orifices.

When the perforated inner liner of a combustor embodying my invention issurrounded with an outer housing defining an air supply passage, as 2 6in Figs. 1-3, it is desirable that the velocity of approach in this airsupply passage be roughly equal to the initial spouting velocity of thejets produced by the orifices. It has been found that velocities of thismagnitude result in efiective cooling of the liner. The maximum velocityof approach is limited by the permissible extent to which the velocityof approach (indicated by the vector V in Fig. 2) produces a deviationof the spouting velocity vector V1 from the exactly radial direction. Itwill be observed in Fig. 2 that the approach velocity V0 gives thespouting velocity V1 a slight axial component toward the left. Thisslight axial component is not harmful to operation of the combustor,since it somewhat tends to increase the flow of air from the initialholes 28 into the tore chamber 36. If on the other hand, the fluid inthe supply passage 26 approached the orifices 28 from the left, then anaxial component of V1 to the right would be produced, which might tendto decrease the amount of air flowing into the tore chamber 36 from theinitial row of jets. With such an ar rangement, it would be necessary todecrease the approach velocity V0, as by increasing the cross sectionarea of the supply passage 26, so as to reduce this axial component ofV1. Otherwise some special means would be needed, for instance thenozzle arrangement of Fig. 10, to eliminate the axial component of thespouting velocity, introduced by the excessive velocity of approach. Afurther factor limiting the maximum value of the approach velocity V0 isthe increase in the overall pressure drop created if the approachvelocity is too high.

Experience in the design of many forms of fluid fuel combustorsembodying my invention has shown that the initial spouting velocity V1produced by the orifices in the liner should be of such a magnitude thatthe velocity head of the jets is roughly equivalent to 1% of the initialtotal head of the fluid approaching the orifices. If the spoutingvelocity is increased above this value, the total pressure lossesthrough the combustor increase; whereas if the spouting velocity isdecreased, the combustion efiiciency decreases by reason of thedecreased strength of the vortex flow path produced. The practicalresult of this decrease in combustion efliciency is that the flamesproduced by the combustor lengthen, and may extend beyond the exit ofthe combustor. It is of course desired that combustion go to completionwithin the combustion space so that a mixture of uniform temperaturewill be produced at the combustor exit. This is particularly importantin a gas turbine powerplant, where it is highly undesirable that flamesreach the turbine nozzles or buckets.

In the operation of any fluid fuel combustor of the general typerepresented by my invention, there appears to be an inherent loss oftotal head of the fluid flowing through the system. Apparently this isat least partly accounted for by the turbulence which it is necessary toproduce in the device in order to secure effective mixing and completeburning. Experience has shown that with my combustion system the overallloss in total head, from the air supply passage approaching the linerorifices to the liner exit is roughly equivalent to the velocity head ofthe fluid jets issuing from the orifices into the combustion space. Asindicated above, this is about 1% of the initial total head of thefluid. Thus a useful rule of thumb is that the total pressure dropinherent in a combustor embodying my invention is that head required toproduce the initial spouting velocity V1. This overall loss is very muchless than that incident to the operation of the best combustors known tothe prior art.

My invention readily lends itself to an almost infinite variety ofarrangements. In Figs. 13 and 14 I have illustrated a form wherein theair, instead of being admitted adjacent the discharge end of thecombustion unit, is admitted adjacent the inlet end in the vicinity ofthe fuel nozzle. In Figs. 13 and 14, 50 and EI indicate inner and outerwalls corresponding to walls It! and I I of Fig. l and 52 indicatesperforated baffle strips corresponding to members I2 of Fig. 1. The airinlet is indicated at 53 and the discharge nozzle at 54. In thisarrangement, walls 50 and 5| converge toward each other from theadmission end to the discharge end, providing an annular plenum chamber'55 which in longitudinal section is tapering. The fuel nozzle isindicated at 56 and the ignition plug at 51. Otherwise, the arrangementmay be the same as that shown in Fig. 1 and the operation is the same.

With respect to the arrangement of the nozzles for supplying the film ofinsulating and cooling air on the inner surfaces of the liner, a greatmany alternate arrangements are possible, Instead of the singletransversely extending nozzles lI between the longitudinal rows of holes28, as in Figs. 1-3, there may be provided a plurality of smaller slotsarranged as shown in Fig. 11. These cooling air nozzles may be formed byproviding a slot I39 in the liner wall and then stamping the liner walloutwardly, downstream from this slot, so as to provide the dimplesindicated at I 3| in Fig. 11. These dimples with the slit orifice attheir upstream side are arranged in groups between the longitudinal rowsof air inlet holes 28.

A still further step in the development of the nozzle arrangements forproviding the cooling and insulating film is shown in Fig. 12. Here theliner is made up of a plurality of coaxial cylindrical segments I32,I33, I34, I35, and I36. Each seg ment is of slightly greater diameterthan the adjacent upstream segment and has an end portion in telescopingrelation therewith. The segments are supported in concentric relation bymeans of struck-out dimples I31, a plurality of which are equally spacedcircumferentially around the outer surface of each segment where itprojects into the next adjacent larger diameter segment. Theseprojections I37 may of course be spot-welded to the next succeedingsegment so that the set of segments forms an integral liner. The linermay be supported within the outer housing II by means of perforatedradially extending bafiles I2, which are similar in structure andpurpose to the baffles I2 of Fig. 1. With this arrangement, thetelescoping portions of the liner segments form substantially continuousannular slots I38, which serve as orifices for forming the film ofcooling and insulating air on the inner surface of the next succeedingsegment, as indicated by the arrows in Fig. 12. It will be observed thatthe air inlet ports 280, which furnish the primary air to the initialmixing and ignition chamber defined by segment I32 are located inSegments I32 and I33. The openings 281) which furnish the secondary airare arranged in segments I35 and I36, these secondary openings beingseparated from the primary air openings by the imperforate segment 134.

In carrying out my invention, suitable fuel injecting means other thanthat illustrated in the drawings may be employed; Any ofv the wellknowntypes of mechanical atomizing nozzles may be used, such as the highpressure nozzles used in diesel engine fuel injection systems. Suchnozzles require pressures in the neighborhood of 2,000 lb./in. toproduce effective atomization of the fuel oil. The pressure required maybe greatly reduced by the use of the well-known simple vortex nozzlewhich requires pressures in the neighborhood of 5 to 400 1b./in. A veryconsiderable increase in the range, and improvement in other operatingcharacteristics of the combustor, can be obtained by use of theso-called duplex nozzle. This general typeof nozzle is disclosed in theUnited States patent to Nightingale, 1,873,781, issued August 23, 1932.An especially advantageous arrangement for the duplex nozzle isdisclosed in a copending application Serial No. 622,604, filed October16, 1945, in. the name of Charles D. Fulton, now Patent No. 2,590,853.Also, a nozzle of the air-atomizing" typemay be employed, in which astream of high-pressure air helps to break up the liquid fuel intosufficiently fine particles. Suitable nozzles of this type are disclosedin the co-pending application of B. -O. Buckland and D. C. Berkey,Serial No. 62,634, filed November 30, 1948, now Patent No. 2,595,759,and assigned to the same assignee as the present application. All of theabove-mentioned types of nozzles have been successfully employed inconnection with c'ombustors embodying my invention.

Whatever the type of nozzle used, it is desirable that liquid fuelparticles be introduced into the mixing and ignition chamber 30 with aspray pattern in the form of a hollow cone, as represented in Fig. 2.This is particularly important at low total rates of fuel flow. Thisavoids the projection of liquid fuel particles axially down the liner,and results in the particles being projected substantially transverselyto the flow path of the air circulating in the double opposed vortexflow paths in chamber 30. This arrangement has been found most effectivein producing quick and efiicient mixing of the fuel particles with thecombustion air, so that ignition is readily initiated under difficultconditions. In this'connection it may be noted that the sparking device(Fig. 1) should be so located that the spark gap will lie substantiallyin the surface of the conical spray pattern produced by the fuel nozzle.This insures that fuel will reach the spark gap when the sparking deviceis energized.

At high rates of air flow to the combustor, it it not quite so importantthat the fuel spray be supplied in the form of a hollow cone, for theair velocities in space are then sufficiently great to pick up the fuelparticles and sweep them backward and radially outward as indicated bythe spray paths 36a in Fig. 2, so that no fuel particles are projectedaxially down. the center of the liner at high velocity. Therefore, ifthe device is intended to operate only at high air flows, so that highgas velocities are maintained over the entire operating range, then itbecomes more or less immaterial as to how the fuel particles areintroduced into the chamber 30.

In addition to the ordinary light liquid fuels, such as gasoline,kerosene, it is entirely feasible to use heavy fuel oils, such as that,known commercially as bunker C. Furthermore, alcohol or the specialfuels known to those skilled in the art as 100% aromatics may be used.

I may also utilize solid fuel, such as pulverized coal. In the case ofsolid fuel, such as pulverized coal, fuel may be admitted through thering of openings adjacent to the initial mixing and igniting chamber.Such an arrangement is shown in Fig. 15 wherein indicates the innerwall, 5|v the outer wall, 52 the air admission conduit and 53 the firstring of holes which is adjacent to the mixing and igniting chamber 64.In connection with the first ring of holes 63, there are provided. fuelnozzles 55 through which fuel, such as powdered fuel, may be discharged.into the combustion space. In the presentinstance, two fuel nozzles 55are illustrated, the same being arranged diametrically opposite eachother. Otherwise, the arrangement shown in Fig. 15 may be the sameasthat shown. in Figs. 1 to 5, inclusive.

While pulverized coal is referred to as solid fuel it is to be notedthat powdered solid fuel entrained in a stream of air is. analogous to afluid fuel, and I intend the term fluid fuel to include thisinterpretation.

My invention is well adapted for use in con.- nection with gas turbines.When utilized to drive a turbine wheel, a number of the individual unitsmay be arranged circumferentially around the periphery of a turbinewheel so as to supply gases throughout the circumference of the wheel.Such an arrangement is illustrated in Fig. 15 wherein l0 indicates anumber of'combustion units spaced circumferentially and having theirdischarge ends connected to an annular nozzle box H from which gases maybe fed through suitable nozzles to a turbine wheel.

Such arrangements are more fully disclosed in ccpending applications,Serial No. 506,930, filed in the name of Alan Howard on October 20,1943, now Patent No. 2,479,573, .and Serial No. 525,391, filed March 7,1944, in the name of Dale D. Streid, now Patent No. 2,432,359, both assigned to the same assignee as the present application.

A combustion unit embodying my invention, because of its capacity toinitiate combustion under conditions of relatively high air flow andrelatively low fuel flow, has especially great utility in an arrangementsuch as that shown in Fig. 15. In such arrangements, it is importantthat ready ignition be effected in all the combustion chambers. Instarting up, there is likely to be small time differences for ignitionto take place in the several combustion chambers. As a result, therewill' occur an increase in air flow from the air compressor or othercommon air supply through the combustion chambers not ignited and adecrease in such air flow through the combustion chambers alreadyignited. Thus ignition must be initiated in the not already lightedchambers at a time of relatively large air flow and small fuel flow. Andit is important that it be initiated promptly to maintain safe upperlimits of temperature of the gases coming from the already ignitedcombustion chambers. By my invention, ignition under such conditions isobtained. Also, in the case of a multiplicity of combustion chambers,should some stoppage of fuel in one or a number of them occur, forinstance due to a slug of water in the liquid fuel supply line, causingcombustion to cease, and then the fuel starts flowing again, ignition inany such chamber would be againv effected.

17 simply by turning on the spark ignition even with relatively highrates of air flow.

A further important advantage of combustors incorporating my inventionis that they are capable of operating at combustion space pressures overa wide range, for instance from atmosphere to 8 atmospheres, as may berequired for burning hydrocarbons in air in a high altitude aircraftpowerplant. 'Onthe basis of present knowledge, I believe there is noupper limit of pressure at which my combustion system may be made towork satisfactorily. With specially selected fuels, the lower pressurelimit may be atmosphere or lower. Furthermore, my combustors may operateover extremely Wide ranges in average exit temperature. They may operatewith a minimum temperature rise through the system of only 100 R, up toa maximum on the order of 3000 F. temperature rise, while maintainingefficient, quiet, and stable combustion throughout this extreme range.The rate of air flow over the operating range of the combustor may be onthe order of 30 to l, as for example from 1000 lbs. of air per hour,total flow through one combustor, to a maximum of 36,000 lbs. per hour.

The figures given in the preceding paragraph are for a combustor whichhas a liner about eight inches in diameter and about twenty inches long.Tests have shown that my combustion principles can readily be applied tocylindrical combustors with liners ranging from one to eighteen inchesin mean inside diameter; and I believe that units of larger sizes areentirely feasible.

In Fig. 17 is illustrated a modification wherein, instead of using aplurality of units after the manner shown in Fig. 16, I utilize a singleunit which is in the form of an annulus and which is shown as beingutilized to supply gases for operating a turbine wheel. Referring toFig. 17, 80 and Si are concentric spaced walls which define an annularcombustion chamber 82 to which fuel is supplied by one or more fuelnozzles 83. Surrounding walls BI and 80 are two spaced concentric walls84 and 85 which define annular air chambers 86 and 81 from which air issupplied through openings 88 in walls 80 and 8| to the combustionchamber. Air is supplied to chambers 86 and 81 through one or more airsupply conduits 89. At 90 is indicated an annular nozzle arranged todischarge gases to the buckets SI of a gas turbine wheel 92. In Fig. 17,the arrangement is illustrated only diagrammatically. It may embody thevarious details of construction illustrated more specifically in Figs. 1to 15, inclusive.

It will be readily apparent that the annular chamber of Fig. 17 could bedeveloped to form a flat combustor, the walls 80, 8! being plane insteadof annular. Such an arrangement would amount to a plurality of theelemental units represented by Figs. 6, 7 placed in side-by-siderelation.

My invention has made possible heat release space rates hitherto thoughtimpossible with known combustion devices. The maximum rates obtained areon the order of 200 million B. t. u./cu. ft./hr., or upwards of 1,000times that obtained with the mostefiicient modern steam power boilers.The practical fuel rates for gas turbine operation are in theneighborhood of 23/ gallons of a liquid fuel such as kerosene per squareinch of liner cross-section per hour at a combustion space pressure of 4atmospheres.

. 18 Even with such extremely nigh heat release rates, the combustioneificiency approaches very closely to the ideal or perfect condition.

In spite of the enormous heat release rates obtained, the arrangement Ihave provided for cooling the liner is so effective that this criticalpart'may be made of an ordinary commercial stainless steel alloy, suchas that known to the trade as No. 2520, containing 25% chromium, 20%nickel, and the balance iron. Good operation has been obtained withaverage combustor exit temperatures in the neighborhood of 2000" F.,with maximum temperature of 3000 F. at the center of the reaction space,while the temperature of the metal liner remains safely below 1500 F.

While I have shown and described numerous specific embodiments of myinvention, it will be obvious to those skilled in the art that variousadditional modifications may be made without departing from myinvention, and I intend the appended claims to cover all suchmodifications as fall within the true spirit and scope of the invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. A reaction device comprising walls defining a primary mixing zone anda secondary reaction space, said walls including secondary spaced sidewall portions forming an axially elongated sec-' ondary space, theprimary zone being defined between spaced primary side wall portions anda transversely extending end closure wall, means for introducing a firstfluid reactant into the-primary space, the primary side wallportionsdefining at least two transversely spaced exactly opposed fluidinlet nozzles located at a common plane normal to the axis of thereaction space, said plane being spaced from the closed, end wall of theprimary space a distance on the order of .7 times the transverse spacingof said nozzles, and a source of supply of a second fluid reactant underpressure including walls associated'with the primary walls and definingsymmetrical flow paths communicating with the respective nozzles and ofsuch size that substantially radial discrete free jets of the secondfluid issue symmetrically from the nozzles and meet at the axis of thereaction space, with at least a portion thereof flowing axially towardthe closed end wall and thence transversely away from the axis todescribe a uniform symmetrical double opposed spiral path in the primaryspace, the reacting fluids flowing in a generally axial direction pastthe incoming jets to the open end of the reaction space, all inlets forsaid second fluid in the walls defining the primary space producing jetssubstantially tangential to said double opposed spiral flow path.

2. A reaction chamber comprising first and second opposed wall portionsdefining therebetween an axially elongated reaction space, a thirdportion forming a closure for one end of said space, the opposite endbeing open for the discharge of reaction products, means for introducinga first fluid reactant into said space adjacent the closed end of thechamber, and means for introducing a second fluid including opposednozzle means in said first and second wall portions located in a commonplane normal to the axis of the chamber and spaced from the closed endthereof, and means including walls defining passages for supplying asecond fluid uniformly to said nozzle means whereby discrete jets of thesecond fluid issuing from said nozzles meet at the axis of the chamberand thence flow axially with at least a portion of the fluid flowingtoward the closedend of the chamber and then transversely away from theaxis to describe a uniform symmetrical double opposed spiral flow pathin the primary mixing space between the closed end of the chamber andsaid nozzle means, and orifice means in said opposed wall portionsadapted to form a thin protective envelope of flowing fluid over thewall surfaces subject to contact with reaction products.

3. In a reaction chamber the combination of a liner of substantiallycircular cross section closed at one end and open for the discharge ofreaction products at the other end, means for introducing a first fluidreactant into the liner adjacent the closed end thereof, means forintroducing a second fluid comprising a plurality of circumferentiallyspaced inlet openings in the wall of the liner located in a common planetransverse to the axis of the liner and spaced from the closed endthereof, and means including walls defining passages for supplying thesecond fluid to said inlet openings uniformly whereby discrete jets offluid produced, by the circumferentially spaced openings meet at theaxis of the liner and thence flow axially with atleast a portion of thefluid flowing axially toward the closed end of theliner and thenradially outward to described a uniform symmetriflowingfluid over thesurfaces subject to con- 1 tact with reaction products.

4;. In a combustor for burning fluid fuel, the combination of a liner ofsubstantially circular cross section closed at one end and open for thedischarge of hot products of combustion. at theother end, means forintroducing fluid fuel into the liner adjacent the closed end thereof,means for introducing combustion air comprising a plurality ofcircumferentially spaced air inletopenings in the wall of the linerlocated in a common plane transverse to the axis of the liner and spacedfrom theclosed end of the liner, and means for supplying, combustion airto said inlet openings in such a manner that discrete jets of airproduced by the circumferentially spaced openings meet at the axis ofthe liner and thence flow axially with at least a portion of the airflowing axially toward the closed end of the liner and then radiallyoutward to describe a uniform symmetrical substantially toroidal path,and orifice means associated with the liner wall and arranged to form athin protective envelope of flowing air over the surfaces subject tocontact with hot products of combustion to prevent deposition ofcarbonized particles thereon.-

5. In a combustor for burning fluid fuel, combination of a liner ofsubstantially circular cross section closed at one end and open forthedischarge of hot products of combustion at the other end, fluid fuelspraying nozzle means adjacent the central portion of the closed end andadapted to deliver fuel particles into the liner with a spray patternsubstantially in the form of a. hollow cone coaxial with the liner, saidliner having a plurality of combustion air inlet holes let holesadjacent the closed end of the liner in the area subject to directimpingement by fuel particles in the spray pattern, and means forsupplying combustion air to said inlet openings uniformly so thatdiscrete jets produced by the openings in each circumferential row meetat the axis of the liner and thence flow axially with at least a portionof the air fromthe circumferential row of holes nearest the nozzle endof the liner flowing axially towards the nozzle and then radiallyoutward to pick up and mix with the fuel particles in the spray pattern.

6 In a combustor for burning fluid fuel, the combination of a liner ofsubstantially circular cross section closed at one end and open for thedischarge of hot products of combustion at the other end, fluid fuelspraying nozzle means adjacent the centralportion of the closed end andadapted to deliver fuel particles into theliner with a spray patternsubstantially in the form of a hollow cone coaxial with the liner, saidliner having aplurality of combustion air inlet holes arranged incircumferential rows, each row lying in a common plane transverse to theaxis of the liner with corresponding holes in the respective rowsarranged in a straight substantially longitudinal row, there being nocombustion air inlet holes adjacent the closed end of the liner in thearea subject to direct impingement by fuel particles in the spraypattern, and means for supplying combustion air to said inlet openingsuniformly so that discrete jets produced by the openings in eachcircumferential row meet at the axis of the liner and thence flowaxially with at least a portion of the air from the circumferentialrowof opening nearest the nozzle flowing axially toward the nozzle and thenradially outward across the fuel spray pattern.

7. In a combustor for burning fluid fuel, the combination of a liner ofsubstantially circular cross section closed at one end and'open for thedischarge of hot products of combustion at the other end, fluid fuelspraying nozzle means adjacent thecentral portion of the closed end and4 adapted. to deliver fuel particles into the liner with a spray patternsubstantially in the form of a hollow cone coaxial with the liner, saidliner having a plurality of combustion air inlet holes arranged incircumferential rows, each row lying in a common plane transverse to theaxis of the liner with corresponding holes in the respective rowsarranged in a straight substantially longitudinal row, there being nocombustion air inlet holes at the nozzle end of the liner in the areasubject to direct impingement by fuel particles in the spray pattern,means for supplying combustion air to said inlet openings uniformly sothat discrete jets produced by the openings in each circumferential rowmeet at the axis of the liner and thence flow axially with at least aportion of the air from the circumferential row of openings nearest thenozzle flowing axially toward the nozzle and then radially outwardacross the fuel spray pattern, and orifice means associated with theliner wall and arranged to form a thin protective envelope of flowingair over the surfaces subject to contact with hot products of combustionto prevent deposition of carbonized particles thereon.

8. In a combustor for burning fluid fuel, a substantially cylindricalliner closed at one end and open for the discharge of hot products ofcombustion at the other end, the closed end and adjacent portion of theliner defining a primary air and fuel mixing and ignition space havingno p ngs for the admission of combustion air,

fluid fuel spraying nozzle means adjacent the central portion of theclosed end and adapted to deliver fuel particles into the primary mixingand ignition space with a spray pattern substantially in the form of ahollow cone coaxial,

with and intersecting that portion of the liner wall defining saidprimary space, the remainder of the liner defining a secondarycombustion space adjacent said first space and having a plurality ofcircumferential rows of combustion air inlet openings, eachcircumferential row lying in a common plane transverse to the axis ofthe liner with corresponding holes in the respective rows arranged in astraight substantially longitudinal row, means for supplying combustionair to said inlet openings uniformly so that discrete jets produced bythe openings in the circumferential rows nearest the closed end of theliner meet at the axis of the liner and thence flow axially with atleast a portion of the air flowing axially toward the nozzle and thenradially outward and across the fuel spray pattern in the mixing andignition space.

9. A combustion unit comprising an annular wall shaped to define adischarge opening at one end, a head which closes the other end, saidwall being provided with rings of circumferentially spaced openings, theseveral rings of openings being spaced axially from each other and thering of openings nearest the head being spaced from the head to form aninitial mixing and ignition chamber adjacent said head to which primarycombustion air is supplied by axial flow of air from the radial jetsformed by the spaced openings next to said mixing and ignition chamber,a fuel supply means adjacent the center of the head which directs fuelinto said mixing and ignition chamber in the form of a substantiallyhollow conical spray at an angle to the direction of air flow thereinwhereby the fuel and air are mixed initially in said mixing and ignitionchamber and then flow axially toward said discharge end through thespaces defined between said circumferentially spaced radial jets.

10. A combustion unit comprising an annular wall shaped to define adischarge opening at its one end, a head which closes the other end,said wall being provided with rings of circumferentially spacedopenings, the several rings of openings being spaced axially from eachother and the ring of openings nearest the head being spaced from thehead to form an initial mixing and ignition chamber adjacent said headto which primary combustion air is supplied by axial flow of air fromthe radial jets formed by the spaced openings next to said mixing andignition chamber, and a fluid fuel nozzle in said head adapted to directfuel in the form of a substantially hollow conical spray outward towardthe wall of said mixing chamber with a small axial component ofvelocity, the air flowing axially into said mixing and ignition chamberpicking up the fuel in such chamber, mixing with it and then carrying itaxially through the spaces defined between said circumferentially spacedradial jets to said discharge opening.

11. A combustion unit comprising an annular wall shaped to define adischarge opening at one end, a head which closes the other end, saidwall being provided with rings of circumferentially spaced openings, theseveral rings of openings being spaced axially from each other and thering of openings nearest the head being spaced from the head to form aninitial mixing and ignition chamber adjacent said head to which primarycombustion air is supplied by axial fiow of air from the radial jetsformed by the spaced openings next to said mixing and ignition chamber,a fuel supply means adjacent the center of the head which directs fuelinto said mixing and ignition chamber in the form of a substantial- 1yhollow conical spray at an angle to the direction of air flow thereinwhereby the fuel and air are mixed initially in said mixing and ignitionchamber and then flow axially toward said discharge end through thespaces defined between said circumferentially spaced radial jets, andmeans for directing an envelope of air along the innersurface of saidwall to prevent carbon from depositing thereon.

12. A combustion unit comprising an annular wall shaped to define adischarge opening at one end, a head which closes the other end, saidwall being provided with rings of circumferentially spaced openings, theseveral rings of openings being spaced axially from each other and thering of openings nearest the head being spaced from the head to form aninitial mixing and ignition chamber adjacent said head to which primarycombustion air is supplied by axial flow of air from the radial jetsformed by the spaced openings next to said mixing and ignition chamber,a fuel supply means adjacent the center of the head which directs fuelinto said mixing and ignition chamber in the form of a substantiallyhollow conical spray at an angle to the direction of air flow thereinwhereby the fuel and air are mixed initially in said mixing and ignitionchamber and then flow axially toward said discharge end through thespaces defined between said circumferentially spaced radial jets, andmeans for directing an envelope of air along the inner surfaces of saidwall and head to prevent carbon from depositing thereon.

13. A combustion unit comprising spaced coaxial tubular inner and outerwalls which define a combustion chamber and an annular air chambersurrounding the combustion chamber, an end head at one end of the innerwall, the other end being shaped to define a discharge opening, saidinner wall being provided with rows of spaced openings which terminateshort of said end head whereby there is defined in the vicinity of suchhead an initial mixing and ignition chamber, axially extending bafilesin said annular air chamber for directing air flow in the chamber,

said baffles being provided with spaced openings for flow of air, meansfor supplying air to said air chamber at one end of the chamber, andnozzle means for supplying fuel to said mixing and ignition chamberhaving an angle of discharge such that the sprayed fuel is confined tosaid initial mixing and ignition chamber.

14. A combustion unit comprising an annular wall shaped to define adischarge opening at one end, a head which closes the other end, saidwall being provided with rings of circumferentially spaced openings, theseveral rings of openings being spaced axially from each other, and thering nearest the head being spaced from the head a distance of the orderof .7 the diameter of the wall to form an initial mixing and ignitionchamber, means for supplying air uniformly through said rings ofopenings to the space within said wall, means for supplying fuel to saidmixing and ignition chamber, and means for directing an envelope of airalong the inner surfaces of said wall and head to prevent carbon fromdepositing thereon.

15. A combustion unit comprising an annular wall shaped to define adischarge opening at one end, a head which closes the other end, saidwall being provided with rings of circumferentially spaced openings, theseveral rings of openings being spaced axially from each other,- andwalls defining slots between the openings for directing an envelope ofair along the inner surface of said first-named wall to prevent carbondeposits from forming thereon.

16. A combustion unit comprising an annular wall shaped to define adischarge opening at one end, a head which closes the other end, saidwall being provided with rings of circumferentially spaced openings, theseveral rings of openings being spaced axially from each other, and thering nearest the head being spaced from the head a distance of the orderof .7 the diameter of the wall to form an initial mixing and ignitionchamber, means for supplying air through said rings of openings to thespace within said wall, and means for supplying fuel in a radialdirection through one or more of the holes of the ring of holes adjacentto such chamber whereby it will be picked up by rearward flow of air andcarried rearwardly into said initial mixing and ignition chamber.

17. A liner for use in a combustor having a fluid fuel spraying nozzleadapted to discharge fuel particles with a spray pattern in the form ofa substantially hollow cone of a known vertex angle, comprising asubstantially cylindrical wall defining an opening for ,the discharge ofhot products of combustion at one end and having a head member closingthe other end, the head end of the liner being provided with an openingfor introducing fuel, the liner wall having a plurality of straightlongitudinal rows of air inlet openings each of a diameter of the orderof onetenth the mean inner diameter of the liner, corresponding holes ineach row being circumferentially spaced at intervals of the order ofoneseventh the circumference of the liner and lying in a common planetransverse to the axis of the liner, the plane of the firstcircumferential row being spaced from the head end at a location beyondthe intersection of the fuel spray cone with the inner surface of theliner, the last circumferential row being spaced axially from the firstrow a distance of the order of one and one-half to two times saiddiameter of the liner, and the axial spacing of the holescenter-tocenter being of the order of one-sixth said diamer of theliner.

18. A liner for use in a fluid fuel combustor comprising a substantiallycylindrical wall defining an opening for the discharge of hot productsof combustion at one end and having a head member closing the other end,the head end of the liner having a portion defining an opening adaptedto receive means for introducing fluid fuel with a spray pattern in theform of a substantially hollow cone coaxial with the liner and having avertex angle of at least degrees, the wall having a plurality ofstraight longitudinal rows of air inlet openings each of a diameter ofthe order of one-tenth the mean inner diameter of the liner,corresponding holes in each row being circumferentially spaced atintervals of the order of one-seventh the circumference of the liner andlying in a common plane transverse to the axis of the liner, the firstcircumferential row being spaced from the head end a distance of theorder of seven-tenths said diameter of the liner, the lastcircumferential row being spaced from the first row a distance of theorder of one and one-half to two times said diameter of the liner, andthe axial spacing of the holes center-to-center being of the order ofone-sixth said diameter of the liner.

ANTHONY J. NERAD.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 710,130 Weiss Sept. 30, 19021,342,901 Good June 8, 1920 1,379,179 Good May 24, 1921 1,650,342 GoodNov. 22, 1927 1,795,347 Reese Mar. 10, 1931 2,072,731 Crosby Mar. 2,1937 2,107,365 Bray Feb. 8', 1938 FOREIGN PATENTS Number Country Date463,942 France Dec. 30, 1913 497,772 France Sept. 24, 1919

